Pc3-4 geomagnetic pulsations at very low latitude in Brazil

Zanandrea, Ademilson; Costa, J. M. Da; Dutra, S. L. G.; Trivedi, N. B.; Kitamura, Teitaro; Yumoto, K.; Tachihara, H.; Shinohara, Masanao; Saotome, Osamu

doi:10.1016/j.pss.2004.08.001

Cited by 8 publications

(6 citation statements)

References 20 publications

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“…These results from the central South American region agree with many previous studies at similar latitudes, based on both ground observations and theoretical models of excitation and propagation of MHD waves that lead to pulsation activity on the Earth's equatorial surface (e.g., Yumoto et al, 1985;Itonaga and Kitamura, 1993;Roy and Rao, 1998;Takla et al, 2011). However, they contradict other studies that showed daytime Pc3 amplification in the equatorial region, without specifying any damping interval (Matsuoka et al, 1997;Zanandrea et al, 2004).…”

Section: Eej Effects On Pulsation Amplitudecontrasting

confidence: 96%

“…The effect of the EEJ appears as a significant increase of amplitude in the horizontal component of diurnal quiet-time geomagnetic variations, Sq (H), but also in a wide range of short-period fluctuations, which can be observed within a few degrees of latitude on the ground. In the typical pulsation period band, the observed equatorial enhancement close to local noon is ~2-3 times when compared with off-equatorial stations, with a proposed fast decrease for periods smaller than 20 s (Sarma and Sastry, 1995;Shinohara et al, 1997;Zanandrea et al, 2004).…”

Section: Introductionmentioning

confidence: 87%

“…The clock of the data recording system was automatically calibrated by global radio signals (LF OMEGA; Saka et al, 1996), which kept the time accuracy within 100 ms during the data acquisition. The stations operated simultaneously from September to November 1994 and their data were previously used in several studies to investigate different characteristics of geomagnetic variations at very low and equatorial latitudes (e.g., Shinohara et al, 1998;Padilha et al, 2003Padilha et al, , 2017Zanandrea et al, 2004;Rastogi et al, 2008). Figure 1 shows a map of South America with the location of the six geomagnetic stations.…”

Section: Geomagnetic Datamentioning

confidence: 99%

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Latitudinal variation of Pc3-Pc5 geomagnetic pulsation amplitude across the dip equator in central South America

Silva¹,

Padilha²,

Alves³

2019

Preprint

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Abstract. In order to clarify the equatorial electrojet effects on ground magnetic pulsations in central South America, we statistically analyzed the amplitude structure of Pc3 and Pc5 pulsations recorded during quiet to moderately disturbed days at multiple equatorial stations nearly aligned along the 10° magnetic meridian. It was observed that Pc3 amplitudes are attenuated around noon at the dip equator for periods shorter than ~ 35 s. It is proposed that daytime Pc3s are related to MHD compressional waves incident vertically on the ionosphere, with the screening effect induced by enhanced conductivity in the dip equator causing wave attenuation. Daytime Pc5s showed amplitude enhancement at all equatorial stations, which can be explained by the model of waves excited at higher latitudes and propagating equatorward in an Earth-ionosphere waveguide. However, a slight depression in Pc5 amplitude compared to neighboring equatorial stations and a phase lag in relation to an off-equatorial station were detected at the dip equator. This result cannot be explained by the ionospheric waveguide model alone and we propose that an alternative propagation model that allows ULF waves to penetrate directly from the magnetosphere to low latitudes could be operating simultaneously to produce these features at the dip equator. Significant effects of the sunrise terminator on Pc3 pulsations were also observed at the stations closest to the dip equator. Contrary to what is reported at other longitudes, in central South America the sunrise effect increases the H-to-D amplitude ratio. We suggest that these differences may arise from the unique characteristics of this sector, with a strong longitudinal variation in the magnetic declination and precipitation of energetic particles due to the presence of the South Atlantic Magnetic Anomaly. The H-component amplification can be explained by enhancements of the zonal electric field near the magnetic equator driven by F-region neutral winds during sunrise.

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Section: Eej Effects On Pulsation Amplitudecontrasting

confidence: 96%

Section: Introductionmentioning

confidence: 87%

Section: Geomagnetic Datamentioning

confidence: 99%

See 1 more Smart Citation

Latitudinal variation of Pc3-Pc5 geomagnetic pulsation amplitude across the dip equator in central South America

Silva¹,

Padilha²,

Alves³

2019

Preprint

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“…To obtain these Pc3 pulsations, we use a band-pass filter applied to the H component. Among the available techniques to filter, the infinite impulse response (IIR) band-pass filter (Balasis et al, 2016, Zanandrea et al, 2004 has been selected because it provides the best performance. The band-pass filter frequency range was 22 -100 mHz (frequency range of the Pc3), where the filtering obtains the best identification of the pulsations of interest.…”

Section: Methodsmentioning

confidence: 99%

Preliminary Pc3-pulsations analysis at conjugate stations using continuous wavelet transform

2021

Proceeding of the 17th International Congress of the Brazilian Geophysical

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“…Consequently, the source and propagation mechanisms of the equatorial and very low latitude pulsations are not fully understood, and they might be related to either upstream waves or mechanisms of pulsations at higher latitudes [Yumoto, 1986;Feng et al, 1995]. Some studies reported an attenuation in the amplitudes of Pc3 pulsation at the dip equator especially for short period Pc3 pulsations [Yumoto et al, 1985;Itonaga and Kitamura, 1993;Roy and Rao, 1998;Takla et al, 2011, Graziela et al, 2020, while other studies reported Pc3 amplitudes enhancement at the dip equator [Sarma and Sastry, 1995;Matsuoka et al, 1997;Saka et al, 2001;Zanandrea et al, 2004]. The dip equator is an imaginary line that roughly passes through the points where a magnetic needle has no dip.…”

Section: Latitudinal Dependence Of Pc3-4 Amplitudesmentioning

confidence: 99%

Latitudinal dependence of Pc3-4 amplitudes across the dip equator along the 210º Magnetic Meridian

Takla,

Maryanto,

Yoshikawa

et al. 2023

Annals of Geophysics

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Studying Pc3-4 geomagnetic pulsations at equatorial and very low latitude regions is an important issue to understand their generation and propagation mechanisms. Pc3-4 amplitudes and their latitudinal dependency across the dip equator up to low latitudes (± 25°) are investigated using geomagnetic data simultaneously obtained by the MAGDAS/CPMN stations along the 210° Magnetic Meridian (MM) chain. Forty-five Pc3 events and thirty-two Pc4 events were selected for this study. Our results show a clear dependence of Pc3-4 amplitudes on geomagnetic latitudes. At the dip equator, most of the selected Pc3 events (~75%) showed an enhancement in amplitudes, while the rest (~25%) showed an attenuation. After that, the amplitudes decreased gradually by increasing latitudes. These results suggest mixed generation and propagation mechanisms for the equatorial and very low latitudes Pc3s. For better understanding, the Interplanetary Magnetic Field (IMF) and solar conditions are examined during the selected events. Results indicate that Pc3 events with enhanced amplitudes at dip equator are mainly occurred in daytime with no preference to IMF (magnitude and direction) and solar parameters, which suggests the ionospheric currents model as a generation and propagation mechanism for these events. While the attenuation observed in the other Pc3 events was associated with intense and abrupt fluctuations in the IMF and solar parameters, which in turn suggests the compressional wave model for generating these Pc3 events. On the other hand, these two models can explain the observed enhancement in the Pc4 amplitudes at the dip equator. Therefore, our obtained results clarified the origin of equatorial Pc3-4 pulsations.

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Pc3-4 geomagnetic pulsations at very low latitude in Brazil

Cited by 8 publications

References 20 publications

Latitudinal variation of Pc3-Pc5 geomagnetic pulsation amplitude across the dip equator in central South America

Latitudinal variation of Pc3-Pc5 geomagnetic pulsation amplitude across the dip equator in central South America

Preliminary Pc3-pulsations analysis at conjugate stations using continuous wavelet transform

Latitudinal dependence of Pc3-4 amplitudes across the dip equator along the 210º Magnetic Meridian

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